When a vehicle is operated during blizzard, snow, sleet, or other icy conditions, precipitation may not be cleared away because the wiper blade becomes encrusted with ice and snow build-up, whereupon the blade is pushed away from the glass by said build-up. The vehicle defroster is incapable of heating the windshield sufficiently to melt the ice forming on the blade and its associated mountings. When ice builds upon the wiper blade, the wiper blade edge no longer has contact with the windshield. Thus the blade cannot perform the intended function of wiping precipitation from the windshield ultimately severally reducing visibility and safety.
There have been a variety of attempts to improve the wiping action of a windshield wiper to clean the outer surface of a windshield in cold weather.
U.S. Pat. No. 4,152,808 discloses a heating element 0.125" wide and 0.005" thick embedded in the sides of a frame adapted to receive a wiper blade. In the upward direction, heat is transferred to the frame and linkage elements. In the downward direction, heat is transferred from the element to the frame, from the frame through a gap in the wiper body carrying the blade and finally down to the blade. In the outward lateral direction, heat is transferred to the surrounding air and essentially wasted. This indirect heating method is accordingly ineffective, inefficient, and limits the flexibility of the blade, thereby inhibiting the blade wiping action.
U.S. Pat. No. 4,497,083 discloses a heated windshield wiper blade having a resistance wire running along the length of the wiper arm, the blade carrier and the wiper blade to heat the blade and the carrier when it is connected to a vehicle's electrical system. The path through which the resistance wire travels and its various connections is quite complex in order to provide the blade with heat.
U.S. Pat. No. 4,360,941, discloses a second, rather complex windshield wiper assembly which incorporates a weather protective hood utilizing electrical conductors affixed on the outer wall of the hood and other conductors affixed on the inner wall of the hood to heat the hood and frame to prevent the accumulation of ice.
U.S. Pat. No. 5,325,561 discloses an unnecessarily complex and inefficient circuitry system. The heating element consists of straight wire which is less than 1/3 of the width of the passageway. Thus the heating element can lie on the passageway causing hot spots and decreasing efficiency and causing blade damage. The probability of a thin straight wire is more prone to breakage or failure.
The devices disclosed in the aforementioned patents leave much to be desired from the standpoint of simplicity of construction, or are not sufficiently flexible to be used with windshields of any desired lateral or longitudinal curvature; some blade designs cause extremely localized heating placing undue thermal stress on the material of the blade. Some require specialized wiper blade frames and/or wiper arm assemblies.
Accordingly, it is an object of the present invention to provide a simple, low cost wiper blade assembly which is not fatigued by the repeated stresses of recipocation, and is easy to replace and install.
It is a further object of this invention to provide flexible heated wiper blade element suitable for incorporation into new or existing wiper assembles, and able to adapt to use on windshields having most any lateral or longitudinal curvature.
It is yet a further object of this invention to provide a heated wiper blade which permits the wiper blade to conform to the shape of the windshield under snow, sleet or other icy conditions. Thus providing satisfactory wiping performance, while simultaneously removing and keeping the wiper blade, frame and linkage free from interference by ice and snow.